Stent and catheter assembly and method for treating bifurcations

ABSTRACT

An apparatus and method is provided for stenting bifurcated vessels. A proximal angled stent is configured for implanting in a side-branch vessel wherein the proximal angled stent has an angulated portion that corresponds to the angle formed by the intersection of the side-branch vessel and the main vessel so that all portions of the side-branch vessel at the bifurcation are covered by the proximal angled stent. A main-vessel stent is provided for implanting in the main vessel, wherein the main-vessel stent has an aperture or stent cell that aligns with the opening to the side-branch vessel to permit unobstructed blood flow between the main vessel and the side-branch vessel. Side-branch and main-vessel catheter assemblies are advanced over a pair of guide wires for delivering, appropriately orienting, and implanting the proximal angled stent and the apertured stent. In one embodiment, a stent delivery assembly is provided for implanting a Y-shaped stent in a bifurcated vessel. A dual balloon Y-shaped catheter is provided having two expandable members. The catheter is delivered over a guide wire while a restraining member holds the expandable members together for low profile delivery.

This application is a CIP of application Ser. No. 08/910,857, filed Aug.13, 1997 now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to stent deployment assemblies for use at abifurcation and, more particularly, a catheter assembly for implantingone or more stents for repairing bifurcations, the aorto-ostium, andbifurcated blood vessels that are diseased, and a method and apparatusfor delivery and implantation.

2. Prior Art

Stents conventionally repair blood vessels that are diseased and aregenerally hollow and cylindrical in shape and have terminal ends thatare generally perpendicular to its longitudinal axis. In use, theconventional stent is positioned at the diseased area of a vessel and,after placement, the stent provides an unobstructed pathway for bloodflow.

Repair of vessels that are diseased at a bifurcation is particularlychallenging since the stent must overlay the entire diseased area at thebifurcation, yet not itself compromise blood flow. Therefore, the stentmust, without compromising blood flow, overlay the entire circumferenceof the ostium to a diseased portion and extend to a point within andbeyond the diseased portion. Where the stent does not overlay the entirecircumference of the ostium to the diseased portion, the stent fails tocompletely repair the bifurcated vessel. Where the stent overlays theentire circumference of the ostium to the diseased portion, yet extendsinto the junction comprising the bifurcation, the diseased area isrepaired, but blood flow may be compromised in other portions of thebifurcation. Unopposed stent elements may promote lumen compromiseduring neointimalization and healing, producing restenosis and requiringfurther procedures. Moreover, by extending into the junction comprisingthe bifurcation, the stent may block access to portions of thebifurcated vessel that require performance of further interventionalprocedures. Similar problems are encountered when vessels are diseasedat their angled origin from the aorta as in the ostium of a rightcoronary or a vein graft. In this circumstance, a stent overlying theentire circumference of the ostium extends back into the aorta, creatingproblems, including those for repeat catheter access to the vesselinvolved in further interventional procedures.

Conventional stents are designed to repair areas of blood vessels thatare removed from bifurcations and, since a conventional stent generallyterminates at right angles to its longitudinal axis, the use ofconventional stents in the region of a vessel bifurcation may result inblocking blood flow of a side branch or fail to repair the bifurcationto the fullest extent necessary. The conventional stent might be placedso that a portion of the stent extends into the pathway of blood flow toa side branch of the bifurcation or extend so far as to completely coverthe path of blood flow in a side branch. The conventional stent mightalternatively be placed proximal to, but not entirely overlaying thecircumference of the ostium to the diseased portion. Such a position ofthe conventional stent results in a bifurcation that is not completelyrepaired. The only conceivable situation that the conventional stent,having right-angled terminal ends, could be placed where the entirecircumference of the ostium is repaired without compromising blood flow,is where the bifurcation is formed of right angles. In such scenarios,extremely precise positioning of the conventional stent is required.This extremely precise positioning of the conventional stent may resultwith the right-angled terminal ends of the conventional stent overlyingthe entire circumference of the ostium to the diseased portion withoutextending into a side branch, thereby completely repairing theright-angled bifurcation.

To circumvent or overcome the problems and limitations associated withconventional stents in the context of repairing diseased bifurcatedvessels, a stent that consistently overlays the entire circumference ofthe ostium to a diseased portion, yet does not extend into the junctioncomprising the bifurcation, may be employed. Such a stent would have theadvantage of completely repairing the vessel at the bifurcation withoutobstructing blood flow in other portions of the bifurcation. Inaddition, such a stent would allow access to all portions of thebifurcated vessel should further interventional treatment be necessary.In a situation involving disease in the origin of an angulatedaorto-ostial vessel, such a stent would have the advantage of completelyrepairing the vessel origin without protruding into the aorta orcomplicating repeat access.

In addition to the problems encountered by using the prior art stents totreat bifurcations, the delivery platform for implanting such stents haspresented numerous problems. For example, a conventional stent isimplanted in the main vessel so that a portion of the stent is acrossthe side branch, so that stenting of the side branch must occur throughthe main-vessel stent struts. In this method, commonly referred to inthe art as the “monoclonal antibody” approach, the main-vessel stentstruts must be spread apart to form an opening to the side-branch vesseland then a catheter with a stent is delivered through the opening. Thecell to be spread apart must be randomly and blindly selected byrecrossing the deployed stent with a wire. The drawback with thisapproach is there is no way to determine or guarantee that themain-vessel stent struts are properly oriented with respect to the sidebranch or that the appropriate cell has been selected by the wire fordilatation. The aperture created often does not provide a clear openingand creates a major distortion in the surrounding stent struts. Thedrawback with this approach is that there is no way to tell if themain-vessel stent struts have been properly oriented and spread apart toprovide a clear opening for stenting the side-branch vessel.

In another prior art method for treating bifurcated vessels, commonlyreferred to as the “Culotte technique,” the side-branch vessel is firststented so that the stent protrudes into the main vessel. A dilatationis then performed in the main vessel to open and stretch the stentstruts extending across the lumen from the side-branch vessel.Thereafter, the main-vessel stent is implanted so that its proximal endoverlaps with the side-branch vessel. One of the drawbacks of thisapproach is that the orientation of the stent elements protruding fromthe side-branch vessel into the main vessel is completely random.Furthermore the deployed stent must be recrossed with a wire blindly andarbitrarily selecting a particular stent cell. When dilating the mainvessel stretching the stent struts is therefore random, leaving thepossibility of restricted access, incomplete lumen dilatation, and majorstent distortion.

In another prior art device and method of implanting stents, a “T” stentprocedure includes implanting a stent in the side-branch ostium of thebifurcation followed by stenting the main vessel across the side-branchostium. In another prior art procedure, known as “kissing” stents, astent is implanted in the main vessel with a side-branch stent partiallyextending into the main vessel creating a double-barreled lumen of thetwo stents in the main vessel distal to the bifurcation. Another priorart approach includes a so-called “trouser legs and seat” approach,which includes implanting three stents, one stent in the side-branchvessel, a second stent in a distal portion of the main vessel, and athird stent, or a proximal stent, in the main vessel just proximal tothe bifurcation.

All of the foregoing stent deployment assemblies suffer from the sameproblems and limitations. Typically, there is uncovered intimal surfacesegments on the main vessel and side-branch vessels between the stentedsegments. An uncovered flap or fold in the intimal or plaque will invitea “snowplow” effect, representing a substantial risk for subacutethrombosis, and the increased risk of the development of restenosis.Further, where portions of the stent are left unopposed within thelumen, the risk for subacute thrombosis or the development of restenosisagain is increased. The prior art stents and delivery assemblies fortreating bifurcations are difficult to use, making successful placementnearly impossible. Further, even where placement has been successful,the side-branch vessel can be “jailed” or covered so that there isimpaired access to the stented area for subsequent intervention. Thepresent invention solves these and other problems as will be shown.

In addition to problems encountered in treating disease involvingbifurcations for vessel origins, difficulty is also encountered intreating disease confined to a vessel segment but extending very closeto a distal branch point or bifurcation which is not diseased and doesnot require treatment. In such circumstances, very precise placement ofa stent covering the distal segment, but not extending into the ostiumof the distal side-branch, may be difficult or impossible. The presentinvention also offers a solution to this problem.

References to distal and proximal herein shall mean: the proximaldirection is moving away from or out of the patient and distal is movingtoward or into the patient. These definitions will apply with referenceto body lumens and apparatus, such as catheters, guide wires, andstents.

SUMMARY OF THE INVENTION

The invention provides for improved stent designs and stent deliveryassemblies for repairing a main vessel and side-branch vessel forming abifurcation, without compromising blood flow in other portions of thebifurcation, thereby allowing access to all portions of the bifurcatedvessels should further interventional treatment be necessary. Inaddition, it provides an improved stent design and stent delivery systemfor repairing disease confined to the aorto-ostium of a vessel withoutprotrusion into the aorta. The stent delivery assemblies of theinvention all share the novel feature of containing, in addition to atracking guide wire, a second positioning wire which affects rotationand precise positioning of the assembly for deployment of the stent.

The present invention includes a proximal angled stent for implanting ina side-branch vessel adjacent to a bifurcation. The cylindrical membercan have substantially any outer wall surface typical of conventionalstents used, for example, in the coronary arteries. The cylindricalmember of the proximal angled stent has a distal end forming a firstplane section that is substantially transverse to the longitudinal axisof the stent. The proximal end of the stent forms a second plane sectionthat is at an angle, preferably an acute angle, relative to thelongitudinal axis of the stent. The acute angle is selected toapproximately coincide with the angle formed by the intersection of theside-branch vessel and the main vessel so that no portion of the stentedarea in the side-branch vessel is left uncovered, and no portion of theproximal angled stent extends into the main vessel.

A second stent is provided for implanting in the main vessel adjacent toa bifurcation in which a cylindrical member has distal and proximal endsand an outer wall surface therebetween, which can typically be similarto the outer wall surface of stents used in the coronary arteries. Anaperture is formed in the outer wall surface of the apertured stent andis sized and positioned on the outer wall surface so that when theapertured stent is implanted in the main vessel, the aperture is alignedwith the side-branch vessel and the proximal angled stent in theside-branch vessel, providing unrestricted blood flow from the mainvessel through to the side-branch vessel. Deployment of the angled andapertured stents is accomplished by a navel stent delivery systemadapted specifically for treating bifurcated vessels.

In one embodiment for implanting the proximal angled stent, aside-branch catheter is provided in which a tracking guide wire lumenextends within at least a portion of the side-branch catheter, beingdesigned to be either an over-the-wire or rapid exchange-type catheter.An expandable member is disposed at the distal end of the side-branchcatheter. A tracking guide wire is provided for slidable movement withinthe tracking guide wire lumen. A positioning guide wire lumen isassociated with the catheter and the expandable member, such that aportion of the positioning guide wire lumen is on the outer surface ofthe catheter and it approaches the proximal end of the outer surface ofthe expandable member. A stent-positioning guide wire is provided forslidable movement within the positioning lumen. The proximal ends of thetracking and stent-positioning guide wires extend out of the patient andcan be simultaneously manipulated so that the distal end of thestent-positioning guide wire is advanced in the main vessel distal to aside-branch vessel, and the distal end of the tracking guide wire isadvanced into the side-branch vessel distal to the target area. In oneembodiment, the stent-positioning guide wire lumen includes an angulatedsection so that the stent-positioning guide wire advanced in the mainvessel distal to the side-branch vessel results in rotation causing theproximal angled stent to assume the correct position in the side-branchvessel. The positioning lumen functions to orient the stent-positioningguide wire to rotate or torque the side-branch catheter to properlyalign and position the proximal angled stent in the side-branch vessel.

The side-branch catheter assembly is capable of delivering the proximalangled stent, mounted on the expandable member, in the side-branchvessel. The side-branch catheter could also be configured for deliveringa self-expanding proximal angled stent.

The stent delivery system of the present invention further includes amain-vessel catheter for delivering a stent in the main vessel after theside-branch vessel has been stented. The main-vessel catheter includes atracking guide wire lumen extending through at least a portion thereof,and adapted for receiving a tracking guide wire for slidable movementtherein. An expandable member is positioned near the main-vesselcatheter distal end for delivering and implanting a main-vessel(apertured) stent in the main vessel. The main-vessel stent includes anaperture on its outer surface which aligns with the side-branch vessel.A positioning guide wire lumen is associated with the expandable member,and is sized for slidably receiving the stent-positioning guide wire.The stent-positioning guide wire slides within the positioning guidewire lumen to orient the expandable member so that it is positionedadjacent to, but not in, the side-branch vessel with the stent aperturefacing the side-branch ostium.

In one embodiment, both the side-branch catheter and main-vesselcatheter assemblies include the so-called rapid exchange catheterfeatures which are easily exchangeable for other catheters while thetracking and positioning guide wires remain positioned in theside-branch vessel and the main vessel, respectively. In an alternateembodiment, both catheters may be of the “over-the-wire” type.

The present invention further includes a method for delivering theproximal angled and the main-vessel (apertured) stents in the bifurcatedvessel. In one embodiment of the side-branch catheter system(side-branch catheter plus proximal angled stent), the distal end of thetracking guide wire is advanced into the side-branch vessel and distalto the target area. The side-branch catheter is then advanced along thetracking guide wire until the distal end of the catheter is justproximal of entering the side-branch. The distal end of the integrated,stent-positioning guide wire is then advanced by the physician pushingthe guide wire from outside the body. The distal end of thestent-positioning wire travels through the positioning guide wire lumenand passes close to the proximal end of the proximal angled stent andexpandable member and exits the lumen. The wire is advanced in the mainvessel until the distal end is distal to the side-branch vessel. Thecatheter is then advanced into the side branch until resistance is feltfrom the stent-positioning guide wire pushing up against the ostium ofthe side-branch vessel causing the proximal angled stent to rotate intoposition and arresting its advancement at the ostium. Thereafter, theproximal angled stent, mounted on the expandable member, is alignedacross the target area and the angled proximal end of the stent isaligned at the intersection of the side-branch vessel and the mainvessel (the ostium of the side-branch vessel) so that the stentcompletely covers the target area in the side-branch vessel, yet doesnot extend into the main vessel, thereby blocking blood flow. Theexpandable member is expanded thereby expanding and implanting theproximal angled stent in the side-branch vessel. The positioning wireprevents forward movement of the expandable member and proximal angledstent during inflation. Thereafter, the expandable member is deflatedand the side-branch catheter assembly is withdrawn from the patient in aknown rapid-exchange manner. In this embodiment, the side-branchcatheter is designed so that both the side-branch tracking guide wireand main-vessel positioning guide wire can be left in their respectivevessels should sequential or simultaneous high pressure ballooninflation be required in each of the vessels in order to complete thestenting procedure. In other words, the integrated positioning wire canbe unzipped from the proximal 100 cm of the catheter thereby allowing itto act as a rapid exchange wire. Preferably, high pressure balloons areinflated simultaneously in the main vessel and proximal angled stents inorder to avoid deforming one stent by unopposed balloon inflation withinthe other one. This additional step of high pressure balloon inflationis a matter of physician choice. A further advantage of this embodimentis that by waiting to advance the integrated stent-positioning wire outof catheter only when the catheter distal end is near the target area,wire wrapping, encountered in an embodiment utilizing two non-integratedguide wires, is avoided. Utilizing this method, the side-branch vesselcan be stented without the need for stenting the main vessel.

In an aorto-ostial application of the side-branch catheter assembly(side-branch catheter plus proximal angulated stent), the positioningwire is advanced into the aortic root while the tracking wire isadvanced into the right coronary or vein graft whose angulated origin isto be stented. After advancement of the proximal-angled stent, mountedon the expanding member, it is aligned across the target area and theangled proximal end of the stent is aligned at the ostium.

In the event that the main vessel is to be stented (with the stentplaced across the bifurcation site), the proximal end of the main-vesselguide wire is inserted into the distal end of the guide wire lumen ofthe main-vessel catheter. The side-branch wire would be removed from theside branch at this time. The main-vessel catheter would then beadvanced into the body until the catheter is within one cm or so of thetarget site. The distal end of the second (integrated,stent-positioning) guide wire, which resides in the main-vessel catheterduring delivery to the main vessel, is then advanced by having thephysician push the positioning wire from outside the body. The distalend of the stent-positioning wire travels through the positioning guidewire lumen and passes underneath the proximal half of the stent until itexits at the site of the stent aperture or a designated stent cell wherean aperture can be formed. The catheter is then advanced distally untilresistance is felt from the stent-positioning guide wire pushing upagainst the ostium of the side-branch vessel indicating that the stentaperture is correctly facing the side-branch vessel ostium and isaligned with the proximal end of the proximal angled stent. Thereafter,the expandable member on the main-vessel catheter is inflated, therebyexpanding and implanting the main-vessel stent into contact with themain vessel, with the aperture in the stent providing a flow path forthe blood from the main vessel through to the side-branch vessel withoutany obstructions. The expandable member is deflated and the main-vesselcatheter is removed from the body. The main-vessel catheter is designedso that both the main-vessel guide wire and side-branch wire can be leftin their respective vessels should sequential or simultaneous highpressure balloon inflation be required in each of the vessels in orderto complete the stenting procedure. The presence of thestent-positioning wire in the stent aperture permits catheter accessthrough this aperture into the side-branch vessel for balloon inflationto smooth out the aperture in the main-vessel stent. This additionalstep is a matter of physician choice.

Utilizing this method, the main vessel can be stented without the needfor stenting the side-branch vessel. An advantage of this embodiment isthat a major side branch, not diseased and requiring treatment, exitingfrom a main vessel requiring stenting, may be protected by thepositioning wire while the main vessel is stented. If “snowplowing”compromise or closure of the side-branch vessel occurs with main-vesselstenting, then access is already present and guaranteed for stenting ofthe side-branch vessel over the wire already in place in the mannerdescribed above. This will allow confident stenting of a main vesselsegment containing a major side branch. In this usage, only ifcompromise or occlusion of the side branch occurs, will additionalstenting of the side branch be required.

In an alternative embodiment, a main-vessel stent that does not have anaperture on its outer surface is mounted on the main-vessel catheter andis implanted in the main vessel so that it spans the opening to theside-branch vessel. Thereafter, a balloon catheter is inserted through atargeted (non-random) stent cell of the main-vessel stent, which iscentered precisely facing the side-branch ostium, so that the balloonpartially extends into the side-branch vessel. This balloon has trackedover the positioning wire which has been left in place through thetargeted stent cell during and after deployment of the main vesselstent. The balloon is expanded, forming an opening through the stentstruts that corresponds to the opening of the side-branch vessel,providing a blood-flow path through the main vessel and main-vesselstent and into the side-branch vessel. A proximal angled stent mountedon a side-branch catheter is then advanced through the main-vessel stentand the opening formed in the targeted stent cell through to theside-branch vessel. The proximal angled stent is expanded and implantedin the side-branch vessel so that all portions of the side-branch vesselare covered by the stent in the area of the bifurcation. After themain-vessel stent and the side-branch vessel proximal angled stent areimplanted, an uncompromised blood-flow path is formed from the mainvessel through the main-vessel stent and opening into the side-branchvessel, and through the side-branch vessel proximal angled stent.

In another alternative embodiment, a stent having a distal angle isimplanted in the main vessel. In portions of the main vessel havingdisease that approaches and is directly adjacent to the side-branchvessel, a distal angle stent is implanted using the novel catheter ofthe present invention so that the stent covers the diseased area, butdoes not jail or cover the opening to the side-branch vessel.

In another alternative embodiment, a Y-shaped catheter and Y-shapedstent are provided for stenting a bifurcated vessel. In this embodiment,a dual balloon catheter has a Y-shaped stent mounted on the balloons andthe balloons are positioned side by side for easier delivery. Theballoons are normally biased apart, but are restrained and held togetherto provide a low profile during delivery of the stent. A guide wire isfirst positioned in a main vessel at a point distal to the bifurcation.A second guide wire is retained in the catheter in a second guide wirelumen while the catheter is advanced over the tracking guide wire sothat the balloons and stent are distal to the bifurcation. The trackingguide wire is then withdrawn proximally thereby releasing the balloonswhich spring apart. The catheter is withdrawn proximally until it isproximal to the bifurcation. As the catheter is withdrawn proximally,one of the two guide wires is left in the main vessel. The other guidewire is then advanced into the side-branch vessel. The catheter is thenadvanced over both guide wires until the balloons and stent are anchoredin the bifurcation. The balloons are inflated and the stent expanded andimplanted in the bifurcation.

In another aspect of the invention, there is provided an apparatus andmethod for stenting a bifurcated vessel having a bifurcation, a firstvessel branch, and a second vessel branch. A dual balloon Y-shapedcatheter is provided and includes a first expandable member and a secondexpandable member. A first lumen is provided for receiving a restrainingmember. The first lumen extends through at least a portion of thecatheter including the first expandable member. A second lumen isprovided for receiving a guide wire. The second lumen extends through atleast a portion of the catheter including the second expandable member.A Y-shaped stent is mounted on the first and second expandable members.A restraining member is positioned within the first lumen such that thefirst expandable member and the second expandable member are normallybiased apart, but are restrained and held together by the restrainingmember. A guide wire is then positioned distally of the bifurcation inthe first vessel branch. The guide wire is loaded into the second lumen.The catheter is advanced over the guide wire so that the catheter isadvanced proximate the bifurcation. The restraining member can then beretracted proximally until the first expandable member and the secondexpandable member are released and spring apart. A wire is then advanceddistally through the first lumen into the second vessel branch. Thecatheter is advanced distally over the wire and guide wire until theY-shaped stent is positioned at the bifurcation. The Y-shaped stent canthen be implanted by inflating the first and second expandable members.The first and second expandable members are then deflated. The catheter,wire, and guide wire are then withdrawn.

In another embodiment two apertured stents are implanted to cover thebifurcated vessels. A main-vessel stent has a cylindrical shape having aheavy cell density on the distal half and light cell density on theproximal half, and an aperture on its outer surface at the junction atthese two halves. A main-vessel stent is first implanted in the mainvessel so that its aperture aligns with the ostium of the side-branchvessel, thereby covering the main vessel proximally with light celldensity and distally with heavy cell density. A second main-vessel stentis then implanted over a tracking wire into the side branch so that theheavy cell density portion of the stent is implanted in the side-branchvessel, the light cell density is implanted in the main vessel andoverlaps the light cell density of the proximal end of the main-vesselstent, and the aperture faces the main vessel as it departs from theside branch. Combined densities of proximal light cell portions proximalto the bifurcation are similar to the heavy cell densities in each limbdistal to the bifurcation. Respective apertures of each of the twomain-vessel stents are aligned with the respective ostia of both limbsof the bifurcation (main vessel and side branch).

Other features and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a bifurcation in which a prior art “T”stent is in a side-branch ostium followed by the stenting of the mainvessel across the branch ostium.

FIG. 2 is an elevational view of a bifurcation in which “touching” priorart stents are depicted in which one stent is implanted in the sidebranch, a second stent implanted in a proximal portion of the mainvessel next to the branch stent, with interrupted placement of a thirdstent implanted more distally in the main vessel.

FIG. 3 is an elevational view of a bifurcation depicting “kissing”stents where a portion of one stent is implanted in both the side-branchand the main vessel and adjacent to a second stent implanted in the mainvessel creating a double-barreled lumen in the main vessel distal to thebifurcation.

FIG. 4 is an elevational view of a prior art “trouser legs and seat”stenting approach depicting one stent implanted in the side-branchvessel, a second stent implanted in a proximal portion of the mainvessel, and a close deployment of a third stent distal to thebifurcation leaving a small gap between the three stents of an uncoveredluminal area.

FIG. 5A is a perspective view of a stent of the present invention havingan angled proximal end.

FIG. 5B is a side elevational view of the proximal angled stent of FIG.5A depicting the distal end being transverse to the longitudinal axis ofthe stent, and the proximal end at an angle of less than 90°.

FIG. 5C is an elevational view of a bifurcation in which a prior artstent is implanted in the side-branch vessel.

FIG. 5D is an elevational view of a bifurcation in which a prior artstent is implanted in the side-branch vessel, with the proximal end ofthe stent extending into the main vessel.

FIG. 5E is an elevational view of a bifurcation in which the proximalangled stent of the present invention, as depicted in FIGS. 5A and 5B,is implanted in the side-branch vessel.

FIG. 6A is a perspective view depicting the main-vessel stent of thepresent invention in which an aperture is formed on the outer surface ofat least a portion of the stent.

FIG. 6B is a side elevational view of the main-vessel stent of FIG. 6A.

FIG. 7A is an elevational view, partially in section, of a side-branchcatheter assembly depicting the distal end of the catheter with theexpandable member and the second guide wire lumen attached thereto, forreceiving the integrated stent-positioning guide wire, while thetracking guide wire is received by the main guide wire lumen.

FIG. 7B is an elevational view, partially in section, of the catheterassembly of FIG. 7A, in which the stent positioning guide wire isadvanced out of the catheter.

FIG. 8 is an elevational view, partially in section, of a side-branchcatheter assembly depicting an expandable balloon having an angledproximal portion corresponding to the angle of the proximal angledstent.

FIG. 9A is an elevational view of a bifurcated vessel in which aside-branch tracking guide wire has been advanced into a side-branchvessel, with the stent-positioning guide wire remaining within thecatheter until the catheter assembly is just proximal to the side-branchvessel.

FIG. 9B is an elevational view of a bifurcation in which a side-branchtracking guide wire has been advanced through the patient's vascularsystem into a side branch, and a stent-positioning guide wire has beenadvanced through the patient's vascular system and into the main vesseldistal to the ostium of the side-branch vessel.

FIG. 10A is an elevational view of a bifurcation in which theside-branch catheter assembly has been advanced in the patient'svasculature so that the proximal angled stent mounted on the expandablemember is positioned in the target area of the side-branch vessel.

FIG. 10B is an elevational view of the side-branch catheter assembly ofFIG. 10A in which the proximal angled stent has been expanded by theballoon portion of the catheter in the side-branch vessel.

FIGS. 11A-11D are partial elevational views in which the side-branchcatheter assembly of FIG. 10A is used to implant the proximal angledstent in the side-branch vessel where the proximal angled stent isrotated to be properly aligned for implanting in the vessel.

FIGS. 12A-12C depict an elevational view, partially in section, of amain-vessel catheter assembly in which the main vessel stent has anaperture on its outer surface.

FIGS. 12D-12F depict an elevational view, partially in section, of themain-vessel catheter of FIGS. 12A-12C with a ramp to help orient andadvance the guide wire through the aperture in the main-vessel stent.

FIGS. 12G-12I depict an elevational view, partially in section, of analternative embodiment of the main-vessel catheter of FIGS. 12A-12C inwhich the guide wire lumen is angled to pass under the stent and exitthrough the stent aperture.

FIGS. 12J-12L depict an elevational view, partially in section, of analternative embodiment of the main-vessel catheter of FIGS. 12A-12C inwhich a portion of the guide wire lumen passes under the stent.

FIGS. 13A-13E are elevational views, partially in section, depicting themain-vessel catheter assembly of FIG. 12A and the main-vessel stent inwhich two guide wires are used to correctly position the main vesselstent so that the aperture in the stent is aligned with the side-branchvessel.

FIG. 14 is an elevational view of a bifurcated vessel in which theproximal angled stent is implanted in the side-branch vessel and a mainvessel stent is implanted in the main vessel.

FIG. 15 is a perspective view of the main-vessel stent of the presentinvention for deployment in the main vessel, where a targeted stent cellprovides an opening through which a guide wire can pass.

FIGS. 16A-16D are elevational views, partially in section, of a mainvessel catheter having the main vessel stent of FIG. 15 mounted thereon,and its relationship to the guide wire for advancing through a targetedstent cell.

FIG. 17 is an elevational view of a bifurcation in which a main-vesselstent is positioned in a main vessel so that it spans the opening to theside-branch vessel.

FIG. 18 is an elevational view of a bifurcation in which a main-vesselstent is implanted in the main vessel and a balloon catheter ispartially inserted into a side-branch vessel to form an opening throughthe targeted stent cell of the main stent.

FIGS. 19A-19C are elevational views of a bifurcation in which amain-vessel stent is first implanted in the main vessel and a catheterassembly next deploys a proximal angled stent in a side-branch vessel.

FIGS. 19D and 19E are cross-sectional views looking down the side-branchvessel at an expanded main vessel prior art stent in which a random,sub-optimal stent cell was entered and expanded.

FIG. 19F is a cross-sectional view looking down the side-branch vesselat an expanded main-vessel stent of the invention in which propertargeted stent cell was entered and expanded.

FIG. 20A is an elevational view, partially in section, depicting a mainvessel catheter in which the main vessel stent is mounted over apositioning guide wire lumen.

FIG. 20B is an elevational view, partially in section, of a main vesselcatheter depicting the main vessel stent mounted over a section of thepositioning guide wire lumen, with a distal portion of the guide wirelumen associated with the distal tip of the catheter.

FIG. 20C is an elevational view, partially in section, of the catheterof FIG. 20B depicting the positioning guide wire advanced out of thepositioning guide wire lumen.

FIG. 20D is an elevational view, partially in section, depicting amain-vessel stent implanted in the main vessel without jailing orcovering the side-branch vessel.

FIG. 20E is an elevational view, partially in section, depicting themain-vessel catheter of FIG. 20A having a ramp to assist in positioningthe guide wire.

FIG. 20F is an elevational view, partially in section, of a distalangled stent being implanted in the main vessel without jailing theside-branch vessel.

FIGS. 21 and 22 are elevational views, partially in section, depictingan alternative embodiment of the main-vessel catheter of FIG. 20B inwhich the distal end of the guide wire lumen springs away from theexpandable balloon.

FIGS. 23A-23B, 24A-24B, 25A-25B, and 26A-26B, are elevational views ofvarious bifurcations which are indicated for receiving main vessel andside-branch vessel stents deployed by the catheters of the presentinvention.

FIG. 27A is an elevational view, partially in section, depicting analternative embodiment in which a Y-shaped catheter assembly deploys aY-shaped stent in the bifurcation.

FIG. 27B is an elevational view depicting an alternative embodiment inwhich a dual balloon catheter assembly deploys a Y-shaped stent in thebifurcation.

FIG. 28 is an elevational view depicting the Y-shaped catheter assemblyof FIG. 27A in which the stent is mounted on the balloon portions of thecatheter.

FIG. 29A is an elevational view, partially in section of a bifurcationin which the Y-shaped catheter of FIG. 27A is delivering the stent inthe bifurcated area, tracking over the wire that joins the two tipstogether.

FIG. 29B is an elevational view, partially in section, of a bifurcationin which the delivered Y-shaped balloon components have been releasedand spread apart by withdrawal of the tracking wire from the otherballoon tip lumen.

FIG. 29C is an elevational view, partially in section, of the Y-shapeddelivery catheter of FIG. 27A in which the Y-shaped balloon has beenwithdrawn proximal to the bifurcation, leaving the first wire in theright branch.

FIG. 30 is an elevational view, partially in section, of the Y-shapeddelivery catheter of FIG. 27A in which the second guide wire is advancedin to the left branch.

FIG. 31 is an elevational view depicting the Y-shaped catheter of FIG.27A in which the Y-shaped stent is implanted in the side branch and mainvessels of the bifurcation.

FIG. 32 is an elevational view, partially in section, depicting theY-shaped catheter assembly of FIG. 27A in which the Y-shaped stent hasbeen implanted and the balloon portions of the catheter have beendeflated.

FIG. 33 is an elevational view depicting a bifurcated vessel in whichthe catheter of FIG. 27A has been withdrawn after implanting theY-shaped stent.

FIG. 34 is an elevational view depicting a modified stent having anaperture in its sidewall and in which half of the stent has a heavystent cell density while the other half of the stent has a light stentcell density.

FIG. 35 is an elevational view depicting the stent of FIG. 34 combinedto form a stent having a heavy stent cell density in all portions.

FIG. 36A is an elevational view depicting a bifurcation, in which thestent of FIG. 35 has been implanted so that the aperture corresponds tothe side-branch vessel and the stent is implanted in the main vessel.

FIG. 36B is an elevational view depicting a bifurcating vessel in whichthe stent of FIG. 34 has been implanted so that the heavy stent celldensity is in the side-branch vessel and the light cell density is inthe main vessel. The aperture corresponds to the continuing lumen of themain vessel.

FIG. 36C is an elevational view depicting a bifurcated vessel in whichtwo stents of FIG. 34 have been implanted in the side-branch vessel andthe main vessel respectively so that the light stent cell density ofeach overlaps with the light cell density of the other thereby creatingcell density proximal to the bifurcation similar to the heavy celldensity present in each limb distal to the bifurcation.

FIG. 37 is an elevational view, partially in section, depicting anotheralternative embodiment in which a Y-shaped catheter assembly deploys aY-shaped stent in the bifurcation.

FIG. 38 is an elevational view depicting the Y-shaped catheter assemblyof FIG. 37 in which a Y-shaped stent is mounted on the balloon portionsof the catheter.

FIG. 39 is an elevational view, partially in section, of the Y-shapeddelivery catheter and Y-shaped stent of FIG. 38 in which the Y-shapedballoon has been advanced proximate to the bifurcation.

FIG. 40 is an elevational view, partially in section, of the Y-shapeddelivery catheter of FIG. 37 in which a restraining member is advancedinto the left branch.

FIG. 41 is an elevational view depicting the Y-shaped catheter of FIG.37 in which the Y-shaped stent is implanted in the side branch and mainvessels of the bifurcation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention includes an assembly and method for treatingbifurcations in, for example, the coronary arteries, veins, arteries,and other vessels in the body. Prior art attempts at implantingintravascular stents in a bifurcation have proved less thansatisfactory. For example, FIGS. 1-4 depict prior art devices whichinclude multiple stents being implanted in both the main vessel and aside-branch vessel. In FIG. 1, a prior art “T” stent is implanted suchthat a first stent is implanted in the side branch near the ostium ofthe bifurcation, and a second stent is implanted in the main vessel,across the side-branch ostium. With this approach, portions of theside-branch vessel are left uncovered, and blood flow to the side-branchvessel must necessarily pass through the main-vessel stent, causingpossible obstructions or thrombosis.

Referring to FIG. 2, three prior art stents are required to stent thebifurcation. In FIG. 3, the prior art method includes implanting twostents side by side, such that one stent extends into the side-branchvessel and the main vessel, and the second stent is implanted in themain vessel. This results in a double-barreled lumen which can presentproblems such as thrombosis, and turbulence in blood flow. Referring tothe FIG. 4 prior art device, a first stent is implanted in theside-branch vessel, a second stent is implanted in a proximal portion ofthe main vessel, and a third stent is implanted distal to thebifurcation, thereby leaving a small gap between the stents and anuncovered luminal area.

All of the prior art devices depicted in FIGS. 1-4 have variousdrawbacks which have been solved by the present invention.

In one embodiment of the present invention, as depicted in FIGS. 5A, 5Band 5E, proximal angled stent 10 is configured for deployment inside-branch vessel 5. Proximal angled stent 10 includes a cylindricalmember 11 having longitudinal axis 12 which is an imaginary axisextending through cylindrical member 11. Distal end 13 and proximal end14 define the length of cylindrical member 11. First plane section 15 isdefined by a plane section through distal end 13 of the cylindricalmember, and second plane section 16 is defined by a plane sectionthrough proximal end 14 of the cylindrical member. Second plane section16 defines acute angle 18, which is the angle between second planesection 16 and longitudinal axis 12.

In treating side-branch vessel 5, if a prior art stent is used in whichthere is no acute angle at one end of the stent to match the angle ofthe bifurcation, a condition as depicted in FIGS. 5C and 5D will occur.That is, a stent deployed in side-branch vessel 5 will leave a portionof the side-branch vessel exposed, or as depicted in 5D, a portion ofthe stent will extend into main-vessel 6. As depicted in FIG. 5E,proximal angled stent 10 of the present invention has an acute angle 18that approximates the angle formed by the bifurcation 4 of side-branchvessel 5 and main-vessel 6. Thus, acute angle 18 is intended toapproximate the angle formed by the intersection of side-branch 5 andmain-vessel 6. The angle between side-branch vessel 5 and main-vessel 6will vary for each application, and for purposes of the presentinvention, should be less than 90°. If there is a 90° angle between theside-branch vessel and the main vessel, a conventional stent having endsthat are transverse to the stent longitudinal axis, would be suitablefor stenting the side-branch vessel.

The proximal angled stent can be implanted in the side-branch vessel totreat number of angulated ostial lesions including, but not limited to,the following:

1. The ostium of a left anterior descending artery (LAD) where there isa circumflex or trifurcation vessel at less than 90° in its departurefrom the LAD.

2. The ostium of the circumflex artery or a trifurcation in a similarsituation as number 1.

3. The ostium of a sizeable diagonal.

4. The LAD just distal to, but sparing, the origin of a diagonal.

5. The ostium of a circumflex marginal artery with an angulatedtake-off.

6. Disease in the circumflex artery just distal to a marginal take-off,but sparing that take-off.

7. The aorta-ostium of a right coronary artery with an angled take-off.

8. The origin of an angulated posterior descending artery.

9. The origin of an LV extension branch just at and beyond the crux,sparing the posterior descending artery.

10. The ostium of an angulated vein graft origin.

11. Any of many of the above locations in conjunction with involvementof the bifurcation and an alternate vessel.

The proximal angled stent of the present invention typically can be usedas a solo device to treat the foregoing indications, or it can be usedin conjunction with the main vessel stent described herein for stentingthe bifurcation.

In keeping with the invention, as depicted in FIGS. 6A and 6B,main-vessel stent 20 is configured for deployment in main-vessel 6.Main-vessel stent 20 includes cylindrical member 21 having distal end 22and proximal end 23. Main-vessel stent 20 includes outer wall surface 24which extends between distal end 22 and proximal end 23 and incorporatesaperture 25 on outer wall surface 24. Aperture 25 is configured so that,upon expansion, it approximates the diameter of expanded proximal end 14of proximal angled stent 10. When main-vessel stent 20 is implanted andexpanded into contact with main-vessel 6, aperture 25 is aligned withside-branch vessel 5 and proximal end 14 of proximal angled stent,thereby providing an unrestricted blood flow path from the side-branchvessel to the main vessel. Unlike the prior art, the main-vesselcatheter allows selection and positioning of an aperture at theside-branch ostium. Furthermore, it provides for the positioning of aguide wire during main-vessel stent deployment which can be used foradditional intervention if necessary. In the prior art techniques accessto a side-branch is through a randomly selected stent element (“cell”)and is only possible after deployment of the stent. The precisepositioning of aperture 25 is optional and aperture 25 could bepositioned either closer to the proximal or distal end of stent 20.

Proximal angled stent 10 and main-vessel stent 20 can be formed from anyof a number of materials including, but not limited to, stainless steelalloys, nickel-titanium alloys (the NiTi can be either shape memory orpseudoelastic), tantalum, tungsten, or any number of polymer materials.Such materials of manufacture are known in the art. Further, proximalangled stent 10 and main-vessel stent 20 can have virtually any patternknown to prior art stents. In one configuration, proximal angled stent10 and main-vessel stent 20 are formed from a stainless steel materialand have a plurality of cylindrical elements connected by connectingmembers, wherein the cylindrical elements have an undulating orserpentine pattern. Such a stent is disclosed in U.S. Pat. No. 5,514,154and is manufactured and sold by Advanced Cardiovascular Systems, Inc.,Santa Clara, Calif. The stent is sold under the trade name MultiLink®Stent. Such stents can be modified to include the novel features ofproximal angled stent 10 (the angulation) and main-vessel stent 20 (theaperture).

Proximal angled stent 10 and main-vessel stent 20 preferably areballoon-expandable stents that are mounted on a balloon portion of acatheter and crimped tightly onto the balloon to provide a low profiledelivery diameter. After the catheter is positioned so that the stentand the balloon portion of the catheter are positioned either in theside-branch or the main vessel, the balloon is expanded, therebyexpanding the stent beyond its elastic limit into contact with thevessel. Thereafter, the balloon is deflated and the balloon and catheterare withdrawn from the vessel, leaving the stent implanted. Deploymentof the angled and main-vessel stents is accomplished by a novel stentdelivery system adapted specifically for treating bifurcated vessels.The proximal angled stent and the main-vessel stent could be made to beeither balloon expandable or self-expanding.

In one embodiment for delivering the novel stents of the presentinvention, as depicted in FIGS. 7A and 7B, side-branch stent deliveryassembly 30 is provided and includes side-branch catheter 31. Theside-branch catheter includes distal end 32 which is configured fordelivery in the patient's vasculature and proximal end 33 which remainsoutside the patient. First guide wire lumen 34A extends through at leasta portion of side-branch catheter 31 depending on the type of catheterdesired for a particular application. First guide wire lumen 34Apreferably is defined by distal end 34B and side port 34C, which istypical of the so-called rapid-exchange-type catheters. Typically, aslit (not shown) extends from side port 34C to just proximal of theballoon portion of the catheter so that the catheter can be rapidlyexchanged during a medical procedure, as is known.

The expandable member 35, which is typically a non-distensible balloon,has a first compressed diameter for delivery through the vascularsystem, and a second expanded diameter for implanting a stent. Theexpandable member 35 is positioned near distal end 32, and in any eventbetween distal end 32 of first catheter 31 and side port 34C.

Referring to FIGS. 7A and 7B, tracking guide wire 36A, distal end 36B,and proximal end 36C all extend through first guide wire lumen 34A.Tracking guide wire 36A preferably is a stiff wire having a diameter of0.014 inch, but can have a different diameter and stiffness as requiredfor a particular application. A particularly suitable guide wire caninclude those manufactured and sold under the trade names Sport® andIronman®, manufactured by Advanced Cardiovascular Systems, Inc., SantaClara, Calif. Tracking guide wire 36A is sized for slidable movementwithin first guide wire lumen 34A.

Stent delivery assembly 30 further includes second guide wire lumen 39Awhich is associated with expandable member 35. Second guide wire lumen39A includes angle portion 39B and straight portion 39C, and is firmlyattached to outer surface 40 of catheter 31, at a point just proximal toexpandable member 35. Integrated stent-positioning guide wire 41A issized for slidable movement within second guide wire lumen 39A. A slit39D is formed in lumen 39A near its distal end so that the stiff guidewire 41A can bow outwardly as shown in FIG. 7B. The portion of guidewire 41A that bows out of slit 39D will limit the advancement ofcatheter 31 as will be further described infra. Integratedstent-positioning guide wire 41A has distal end 41B, and proximal end41C which extends out of the patient. Again, it is preferred thatintegrated stent-positioning guide wire 41A be a fairly stiff wire aspreviously described, for the reasons set forth below in delivering andimplanting the stents in the bifurcation.

In an alternative embodiment, catheter 31 can have an angled expandablemember 42 as depicted in FIG. 8. The proximal end of the expandablemember is angled to coincide with the angle of proximal angled stent 10(not shown in FIG. 8 for clarity). This embodiment is particularlyuseful in delivering the angled stent since the second guide wire lumen39A, and its angled portion 39B, have the same angle as the stent andthe proximal end of the expandable member.

In further keeping with the invention, as depicted in FIGS. 9A-11D,proximal angled stent 10 is mounted on side-branch catheter 31 andimplanted in side-branch vessel 5. The method of achieving proximalangled stent implantation is as follows.

In keeping with the method of the invention, proximal angled stent 10first is tightly crimped onto expandable member 35 for low-profiledelivery through the vascular system.

In one embodiment of the side-branch catheter system 30 (side-branchcatheter plus proximal angled stent), distal end 36B of guide wire 36Ais advanced into side-branch vessel 5 and distal to the target area,with proximal end 36C remaining outside the patient. The side-branchcatheter 31 is then advanced within a guiding catheter (not shown) alongtracking guide wire 36A until distal end 32 of the catheter is justproximal (about 1 cm) from entering side-branch vessel 5. Up to thispoint, guide wire 41A resides in second guide wire lumen 39A so thatdistal end 41B of the wire preferably is near, but not in, angledportion 39B of guide wire lumen 39A. This method of delivery preventsthe two guide wires from wrapping around each other, guide wire 41Abeing protected by the catheter during delivery. The distal end 41B ofintegrated stent positioning guide wire 41A is then advanced by havingthe physician push proximal end 41C from outside the body. The distalend 41B of the integrated stent-positioning guide wire travels throughguide wire lumen 39A and angled portion 39B and passes close to proximalend 14 of angled stent 10 and expandable member 35 and exits lumen 39B.As guide wire 41A is advanced into, through and out of lumen 39B, thestiffness of the wire causes it to bow outwardly through slit 39D in thedistal portion of lumen 39A. Thus, as can be seen for example in FIGS.9B, 10A, 10B, and 11B-11D, the positioning guide wire bows outwardly anddue to its stiffness, provides a bumper against the ostium of theside-branch vessel to assist in positioning and deploying the stents.The stent-positioning guide wire 41A is advanced in the main vesseluntil distal end 41B is distal to side-branch vessel 5. The catheter isthen advanced into side-branch vessel 5 until resistance is felt fromthe stent-positioning guide wire 41A pushing up against the ostium ofside-branch vessel 5. As previously described, stent-positioning wire41A is relatively stiff, as is tracking guide wire 36A, so that they canproperly orient side-branch catheter 31 as it is advanced intoside-branch vessel 5. Angled portion 39B of second guide wire lumen 39Ais angled to assist in rotating the side-branch catheter into properposition into the side-branch vessel. If the stent approachesside-branch vessel 5 in the incorrect position, as depicted in FIGS.11A-11D, stent-positioning wire 41A would be forced to make a very acuteangle. The wire stiffness, however, prevents this from happening andcauses the wire to assume the position of least stress. To relieve thisstress buildup, wire 41A creates a torque on angled portion 39B causingguide wire lumen 39A and side-branch catheter 31, with proximal angledstent 10, to rotate into the correct position. Preferably, slit 39D isformed on catheter 31 outer surface near angled portion 39B so thatstent-positioning guide wire 41A can bow outwardly out of slit 39Dthereby increasing the ability to torque the catheter and the proximalangled stent.

Thereafter, proximal angled stent 10 mounted on the expandable member 35is aligned across the target area, and viewed under fluoroscopy, theacute angle 18 on the proximal end of the proximal angled stent isaligned at the intersection of side-branch vessel 5 and main-vessel 6(the ostium of the side-branch vessel) so that the proximal angled stentcompletely covers the target area in side-branch vessel 5, yet does notextend into the main-vessel 6, thereby compromising blood flow. Theexpandable member 35, which is typically a non-distensible balloon, isexpanded by known methods, thereby expanding the proximal angled stentinto contact with side-branch vessel 5, and thereby implanting theproximal angled stent in the side-branch vessel. Thereafter, expandablemember 35 is deflated and side-branch catheter assembly 31 is withdrawnfrom the patient's vasculature. The side-branch catheter 31 is designedso that both tracking guide wire 36A and stent-positioning guide wire41A can be left in their respective vessels should sequential orsimultaneous high pressure balloon inflation be required in each of thevessels in order to complete the stenting procedure. In other words, theintegrated positioning wire can be unzipped through the slit (not shown)from the proximal 100 cm of the catheter thereby allowing it to act as arapid exchange wire. Preferably, high pressure balloons are inflatedsimultaneously in the main vessel and proximal angled stents in order toavoid deforming one stent by unopposed balloon inflation within theother one. This additional step is a matter of physician choice.Utilizing this method, side-branch vessel 5 can be stented without theneed for stenting the main vessel, as shown in FIGS. 11A-11D.

If necessary, main-vessel 6 also can be stented after stenting theside-branch vessel. In that regard, and in keeping with the invention,main-vessel catheter assembly 50 is provided for implanting main-vesselstent 20, as depicted in FIGS. 12A to 13E. In one embodiment, as shownin FIGS. 12A-12C, main-vessel catheter 50 includes distal end 51 whichis configured for advancement within the patient's vasculature, andproximal end 52 which remains outside the patient. The main-vesselcatheter includes guide wire lumen 53A having distal end 53B and sideport 53C, which is proximal to the balloon portion of the catheter. Sideport 53C is provided in a so-called rapid-exchange catheter system whichincludes a slit (not shown) as is known in the art. Expandable member 54is located near distal end 51 of main-vessel catheter 50. Typically,expandable member 54 is a non-distensible balloon of the type known inthe art for delivering and expanding stents.

In further keeping with the invention, positioning guide wire lumen 55Ais positioned partly on the catheter shaft and partly on expandablemember 54, and is configured for slidably receiving integratedstent-positioning guide wire 56A. Prior to stent delivery, guide wire56A resides in guide wire lumen 55A and only during stent delivery is itthen advanced into and through angled portion 55B of the lumen.

Other embodiments for implanting main-vessel stent 20 in main-vessel 6are depicted, for example, in FIGS. 12D-12F. This embodiment isidentical to that depicted in FIGS. 12A-12C, with the addition of ramp57 which is mounted on balloon 54 and provides a slight incline forguide wire 56A as it exits guide wire lumen 55A. As the guide wireslides along ramp 57, distal portion 56B of the guide wire will moveradially outwardly which helps position the guide wire and orient itinto the side-branch vessel. In another embodiment for implanting themain-vessel stent in the main vessel, as depicted in FIGS. 12G-12I,guide wire lumen 55A passes underneath main-vessel stent 20 and on topof balloon 54. The distal end 55B curves along the balloon so that asguide wire 56B advances out of the distal end 55B of the lumen, it istravelling radially outwardly so that it can more easily locate andadvance into the side-branch vessel 5.

In still another embodiment for implanting main-vessel stent 20 in themain-vessel 6, as depicted in FIGS. 12J-12L, guide wire lumen 55A ispositioned under stent 20 and terminates at distal end 55B in the middleof aperture 25. The distal end 55B of the guide wire lumen will springoutwardly which facilitates advancing guide wire distal end 41B into theside branch vessel. A distal guide wire lumen 58 is attached to theballoon 35 outer surface and extends from aperture 25 to essentially thedistal end of the catheter.

In one method of implanting main-vessel stent 20 in main-vessel 6, asdepicted in FIGS. 12A-12I and 13A-13D, guide wire 41A remains inposition in main-vessel 6, while the side-branch guide wire 36A iswithdrawn from the patient. Main-vessel catheter 50 is backloaded ontoguide wire 41A by inserting proximal end 41C of the wire into the distalend of the catheter and into guide wire lumen 53A. Main-vessel catheter50 is advanced over guide wire 41A and viewed under fluoroscopy untilmain-vessel stent 20 is positioned in main-vessel 6, just proximal toside-branch vessel 5. The distal end 56B of the integratedstent-positioning guide wire 56A is then advanced by the physicianpushing on proximal end 56C from outside the body. The distal end 56B ofwire 56A advances into and through positioning guide wire lumen 55A andpasses underneath the proximal end of the main-vessel stent 20 and exitsthe angled portion 55B of the lumen and enters side-branch vessel 5. Themain-vessel catheter 50 is then advanced distally into the main vesseluntil resistance is felt from the stent-positioning guide wire 56Apushing up against the ostium of the side-branch vessel. The stiffnessof stent-positioning guide wire 56A causes the main-vessel catheter 50,with main-vessel stent 20 thereon, to rotate so that aperture 25 isfacing the side-branch vessel 5 ostium and proximal angled stent 10already implanted.

Expandable member 54, which is typically a non-distensible expandableballoon, is inflated thereby expanding main-vessel stent 20 into contactwith main-vessel 6. Aperture 25 correspondingly expands and whenproperly aligned, provides a blood flow path between aperture 25 andproximal angled stent 10 implanted in side-branch vessel 5. As can beseen in FIGS. 12A-12I and 13A-13D, positioning guide wire lumen 55A ispositioned on expandable member 54, such that when the expandable memberis inflated, positioning guide wire lumen 55A does not interfere withimplanting main-vessel stent 20. After the main-vessel stent isimplanted in the main vessel, expandable member 54 is deflated, andmain-vessel catheter 50 withdrawn from the patient. As seen in FIG. 14,the bifurcated vessel has been fully covered by the stents, side-branchvessel 5 is covered by proximal angled stent 10, and main-vessel 6 iscovered by main-vessel stent 20, so that no portion of bifurcation 4 isleft uncovered and there is no overlap in the implanted stents.

In an alternative method of implanting main-vessel stent 20 inmain-vessel 6 as depicted in FIGS. 12J-12L, tracking guide wire 41A isadvanced through guide wire lumen 55A and guide wire lumen 58 so that itadvances distally of the distal end 51 of the catheter. Thus, guide wiredistal end 41B is advanced into the main vessel so that it is distal ofthe side-branch vessel. Guide wire 56A, which until this point hasremained within guide wire lumen 53A (see FIG. 12K), is advanceddistally as depicted in FIG. 12L and advanced into the main vesseldistally of the side-branch vessel. Guide wire 41A is then withdrawnproximally through guide wire lumen 58 until guide wire distal end 41Bis able to exit guide wire lumen distal end 55B, as shown in FIG. 12L.Since guide wire lumen 55B is preformed and has bias, it will springoutwardly. Guide wire 41A can then be advanced into the side-branchvessel for further positioning. As the catheter 50 is advanced over theguide wires, distal portion 41B of the guide wire will push against theostium of the side-branch vessel thereby insuring the location ofmain-vessel stent 20, and importantly aperture 25 will align with theopening to the side-branch vessel 5.

A non-angulated stent (see FIG. 15) can be implanted using the cathetersystem of FIGS. 7A-11D for stenting a side-branch vessel having anorigin approaching 90° in its takeoff from the main vessel. In thiscircumstance the positioning wire serves solely to arrest the forwardmovement of the stent precisely at the origin of the vessel for moreprecise positioning. However, acute angle 18 is appropriate for abifurcated vessel 4 in which the angulation is acute angle 18, or lessthan 90°. Thus, consideration could be given to standard 30°, 45°, and60° angled stent designs for proximal angled stent 10, which shouldprovide sufficient luminal wall coverage when keeping with the presentinvention. Proximal angled stent 10 has a wide range of applicabilityand can be used for stenting ostial side-branch lesions, ostialcircumflex or left anterior descending (LAD) lesions where thebifurcation is an acute angle, or less than 90°, and ostial lesionsinvolving the angulated origin of a right coronary or vein graft.Importantly, the stents of the present invention provide full coverageof the ostial intimal without protruding into the main vessel or withoutcompromising subsequent access to the distal portion of the main vessel.

In order to assist in properly aligning both proximal angled stent 10and main-vessel stent 20 in side-branch vessel 5 and main-vessel 6,respectively, positioning guide wire lumen 39A, on side-branch catheter31, and guide wire lumen 55A, on main-vessel catheter 50, can beradiopaque, or have a radiopaque marker associated therewith so thatthey are visible under fluoroscopy. Thus, when advancing side-branchcatheter 31 and main-vessel catheter 50, the proper orientation can bemore easily determined by viewing the position of positioning guide wirelumen 39A in connection with main-vessel 6 or positioning guide wirelumen 55A in connection with aligning aperture 25 with side-branchvessel 5. Additionally, positioning guide wire 56A for positioningmain-vessel stent 20 and positioning guide wire 41A for positioningangled stent 10 are either radiopaque or have radiopaque portions, suchas gold markers, to assist in positioning and orienting the cathetersand stents during implantation and deployment.

While the foregoing description includes implanting proximal angledstent 10 in side-branch vessel 5 prior to implanting main-vessel stent20 in main-vessel 6, in an alternative embodiment, the implantingprocedure can be reversed. However, it should be understood that byimplanting main-vessel stent 20 in main-vessel 6, and subsequentlyimplanting proximal angled stent 10 in side-branch vessel 5, aperture 25must be carefully aligned with side-branch vessel 5 so that side-branchcatheter 31 can be advanced through expanded main-vessel stent 20 andaperture 25 and into side-branch vessel 5 for implanting proximal angledstent 10.

While side-branch catheter 31 and main-vessel catheter 50 have beendescribed herein as being of the rapid-exchange type, they also can beof a conventional over-the-wire-type catheter. In over-the-wire-typecatheters, the guide wire lumen extends from the distal end of thecatheter to the proximal end with no side port as is found in therapid-exchange-type catheters. Typical of over-the-wire-type cathetersis the type disclosed in U.S. Pat. Nos. 4,323,071 and B1 4,323,071,which are incorporated herein by reference, and are commonly assignedand commonly owned by Advanced Cardiovascular Systems, Inc., SantaClara, Calif.

In one embodiment of the invention, as depicted in FIG. 15, main-vesselunmodified stent 60 can be configured without the side aperture 25 ofstent 20. Upon expansion, the individual strut members 61 of unmodifiedstent 60 expand sufficiently to permit a balloon catheter to be insertedtherethrough, and expanded, to form an aperture which corresponds to theopening to side-branch vessel 5.

In one method of stenting the bifurcation, side-branch vessel 5 is firststented as described, for example, in the manner shown in FIGS. 9Athrough 11D. Thereafter, main-vessel 6 is stented with unmodifiedmain-vessel stent 60, which does not have an aperture formed in the sideof the stent. As shown in FIGS. 15-18, unmodified stent 60 is mounted onexpandable portion 54 of main-vessel catheter 50. Main-vessel catheter50 is backloaded onto the proximal end of guide wire 41A which isalready in position in the main vessel. Main-vessel catheter 50 isadvanced over the guide wire and viewed under fluoroscopy until stent 60is positioned in the main vessel about one cm proximal to theside-branch vessel. The distal end 56B of integrated stent-positioningguide wire 56A is then advanced by the physician by pushing the proximalend 56C from outside the body. The distal end 56B of wire 56A travelsthrough guide wire lumen 55A and passes underneath the proximal end ofunmodified stent 60 and exits the angled end of the lumen 55B and entersside-branch vessel 5. The main-vessel catheter 50 is then advanceddistally into the main vessel until resistance is felt from thestent-positioning guide wire 56A pushing up against the ostium ofside-branch vessel 5. The stiffness of stent-positioning guide wire 56Acauses the main-vessel catheter 50 with unmodified stent 60 to rotate soa stent cell 62 is precisely facing the side-branch vessel 5 ostium.Expandable member 54 is expanded by known means so that unmodified stent60 expands into contact with main-vessel 6. Expandable member 54 is thendeflated, catheter 50 is withdrawn from the patient's vascular system,leaving guide wire 56A in the side branch.

At this point, proximal angled stent 10 is implanted in the side-branchvessel and unmodified main-vessel stent 60 is implanted and extendsacross side-branch vessel 5. In order to provide an opening inunmodified main-vessel stent 60 that aligns with the opening to theside-branch vessel, third catheter 65, which can be a standard PTCAcatheter, is backloaded onto guide wire 56A, already in side-branchvessel 5, and advanced within the patient's vascular system over theguide wire. As shown in FIG. 18, distal end 66 of catheter 65 isadvanced over guide wire 56A until the distal end 66 of catheter 65begins to pass through cell 62 of unmodified main-vessel stent 60 andenter side-branch vessel 5. Catheter 65 can be of a known type used inangioplasty, as described above, having a non-distensible member orballoon 67. Once balloon 67 is positioned through stent cell 62 and inthe opening of side-branch vessel 5, it is expanded, thereby expandingsome of struts 61 comprising unmodified stent 60 and forming asubstantially circular opening from main-vessel 6 through unmodifiedstent 60 and into side-branch vessel 5. In essence, balloon 67 spreadsapart some of the struts of unmodified stent 60 to form an opening instent 60 that corresponds to the opening to side-branch vessel 5,thereby providing a clear blood flow path between the main vessel andthe side-branch vessel.

Unmodified main-vessel stent 60 is positioned such that it crosses theopening to side-branch vessel 5. As set forth above, a particularly wellsuited stent for this embodiment includes a stent distributed under thetrade name MultiLink® Stent, manufactured by Advanced CardiovascularSystems, Inc., Santa Clara, Calif. By implanting unmodified main-vesselstent 60 in main-vessel 6 with an appropriate stent cell preciselyaligned with the side-branch ostia, dilatation through this same cellover wire 56A assures a fully expanded and non-distorted cell at theostium of side-vessel 5.

In an alternative embodiment, as shown in FIGS. 19A-19C, unmodifiedstent 60 is implanted first, then the side-branch proximal angled stent10 is implanted. In one method of deploying unmodified stent 60, theunmodified stent 60 can be mounted on expandable portion 54 ofmain-vessel catheter 50. Main-vessel catheter 50 is backloaded onto theproximal end of guide wire 41A. Main-vessel catheter 50 is advanced overguide wire 41A and viewed under fluoroscopy until unmodified stent 60 ispositioned in main-vessel 6, proximal to side-branch vessel 5. Thedistal end of the integrated stent-positioning guide wire 56B is thenadvanced by the physician pushing the proximal end 56C from outside thebody. The distal end 56B of wire 56A travels through second guide wirelumen 55A and passes underneath the proximal end of unmodified stent 60and exits the angled end of the lumen 55B and enters side-branch vessel5. The main-vessel catheter 50 is then advanced distally into the mainvessel until resistance is felt from the stent-positioning guide wire56A pushing up against the ostium of the side-branch vessel 5. Thestiffness of stent-positioning guide wire 56A causes the main-vesselcatheter 50 with unmodified stent 60 to rotate so a stent cell 62 isprecisely facing the side-branch vessel 5 ostium. Expandable member 54is expanded by known means so that unmodified stent 60 expands intocontact with main-vessel 6. Expandable member 54 is then deflated, andcatheter 50 is withdrawn from the patient's vascular system, leavingguide wire 56A in side branch 5.

In further keeping with the method of stenting, as shown in FIG. 19B,third catheter 65, which can be a standard PTCA catheter, is backloadedonto guide wire 56A already in side-branch vessel 5 and advanced withinthe patient's vascular system over the guide wire. Distal end 66 ofcatheter 65 is advanced over guide wire 56A until the distal end 66 ofthe catheter begins to pass through struts 61 of stent cell 62 ofunmodified main-vessel stent 60 and enter side-branch vessel 5. Catheter65 can be of a known type used in angioplasty, as described above,having a non-distensible member or balloon 67. Once balloon 67 ispositioned through a stent cell 62 the opening of side-branch vessel 5,it is expanded, thereby expanding some of the struts comprisingunmodified stent 60 and forming a substantially circular opening frommain-vessel 6 through unmodified stent 60 and into side-branch vessel 5.In essence, balloon 67 spreads apart the struts 61 of unmodified stent60 to form an opening in the unmodified stent that corresponds to theopening to side-branch vessel 5, thereby providing a clear opening forfurther stenting side-branch vessel 5.

With the main vessel now stented as depicted in FIGS. 19A-19C,side-branch vessel 5 is stented in the same manner as described in FIGS.9-11. The only difference is that in FIG. 19, unmodified main-vesselstent 60 already is implanted when catheter 31 is advanced intoside-branch vessel 5. Side-branch catheter 31 is backloaded onto guidewire 36A already in side-branch vessel 5. Side-branch catheter 31 isthen advanced until the distal tip of side-branch catheter 31 justenters the side-branch vessel 5 ostium. The distal end 41B of theintegrated guide wire 41A is then advanced by the physician pushing theproximal end 41C from outside the body. The distal end 41B of theintegrated stent-positioning guide wire travels through second guidewire lumen 39A and angled portion 39B and passes close to the proximalend of proximal angled stent 10 and expandable member 35 and exits lumen39B. The stent-positioning guide wire 41A is advanced until the distalend 41B is distal to side-branch vessel 5. The catheter is then advancedinto the side-branch vessel until resistance is felt from thestent-positioning guide wire 41A pushing up against the ostium of theside-branch vessel. As previously described, stent-positioning wire 41Ais relatively stiff, as is tracking guide wire 36A, so that they canproperly orient side-branch catheter 31 as it is advanced into theside-branch vessel. Angled portion 39B of second guide wire lumen 39A isangled to assist in rotating the side-branch catheter into properposition into side-branch vessel 5. If the stent approaches theside-branch vessel in the incorrect position, the stent-positioning wire41A would be forced to make a very acute angle. The wire stiffness,however, prevents this from happening and causes the wire to assume theposition of least stress. To relieve this stress buildup, wire 41Acreates a torque on angled portion 39B causing guide wire lumen 39A andside-branch catheter 31 with proximal angled stent 10 to rotate into thecorrect position. Once the proximal angled stent is positioned inside-branch vessel 5, expandable member 35 is expanded so that theproximal angled stent expands into contact with side-branch vessel 5,making sure that proximal end 14 of proximal angled stent 10 covers andis aligned with the side-branch vessel 5 at bifurcation 4. Proximal end14 is aligned so that it coincides with acute angle 18, thereby ensuringthat all portions of side-branch vessel 5 are covered by the proximalangled stent, where side-branch vessel 5 meets main-vessel 6. Anunobstructed blood-flow path now exists between expanded unmodifiedstent 60 and main-vessel 6 through the opening previously formed andinto side-branch vessel 5 and through implanted proximal angled stent10.

Prior art devices that have attempted to first stent the main vessel andrandomly select a stent cell to expand for alignment with theside-branch vessel, have generally failed. One such approach, known asthe “monoclonal antibody” approach, as depicted in FIGS. 19D and 19E,depict what can happen when an inappropriate target stent cell isselected randomly and then expanded by a high pressure balloon. As shownin FIG. 19D, which is a view looking down side-branch vessel 5 incross-section at a prior art stent 68, the physician randomly selectsstent cell 69 which is a sub-optimal cell to expand with the balloonportion of a catheter. As depicted in FIG. 19E, after balloon expansionin the suboptimal cell 69, entry into the cell with a catheter may beimpossible or, if accomplished, expansion of the balloon may beincomplete. The aperture created will be inadequate and major distortionin the adjacent stent struts may occur. Consequences may includesubacute thrombosis or restenosis. With the present invention, as shownin FIGS. 19A-19C, the target stent cell 62 is the optimal cell forexpansion, and is preselected with a wire in place before stentdeployment (that same wire remaining in place for subsequent access),and is oriented optimally with respect to the side-branch ostium priorto deployment. The resulting expansion as shown in FIG. 19F, guaranteesan optimal aperture where the stent struts have been expanded providinga blood flow path from the main vessel to the side-branch vessel.

In another alternative embodiment for stenting a bifurcation, asdepicted in FIGS. 20A-20C, main-vessel catheter 70 includes expandablemember 71 near its distal end, while the proximal end of the catheter(not shown) is similar to those previously described and can be eitherof the rapid-exchange or over-the-wire types. Catheter 70 includestracking guide wire lumen 72 for slidably receiving tracking guide wire73, lumen 72 extending at least partially through the catheter in therapid-exchange configuration and all the way through the catheter in theover-the-wire configuration. The catheter also includes a positioningguide wire lumen 74 that is associated with the catheter outer surfaceand extends onto and is attached to at least a portion of expandablemember 71. As shown in FIG. 20A, positioning guide wire lumen 74 extendsalong the expandable member and ends just at the distal taper of theexpandable member. As depicted in FIGS. 20B and 20C, positioning guidewire lumen 74 can be formed of two sections, namely distal section 75attached to the distal tip of the catheter, and proximal section 76extending along and attached to the expandable member and the catheter.As previously described, guide wires 73,77 are intended to be relativelystiff wires so that they can more easily maneuver the catheter. In theseembodiments, stent 78 is mounted on the expandable member and overpositioning guide wire lumen 74. Positioning guide wire 77 is configuredfor slidable movement within positioning lumen 74.

In one method of stenting a vessel just proximal to a bifurcation usingmain-vessel catheter 70, tracking guide wire 73 is first positionedwithin the main vessel as previously described. The catheter is thenbackloaded onto the guide wire by inserting the wire into the trackingguide wire lumen 72 and advancing the catheter into the patient'svascular system. At this point, positioning guide wire 77 resides withinpositioning guide wire lumen 74 and is carried into the main vesselwhere it will be released and advanced. Once the catheter has reachedthe target area, positioning guide wire 77 is advanced distally out ofthe positioning guide wire lumen (for FIG. 20A) or pulled back slightlyout of distal section 75 of the positioning guide wire lumen (for FIGS.20B and 20C). Once released by removal of the guide wire, distal section75 will spring out so that the positioning guide wire can seek out andbe advanced into the side-branch vessel. Once the positioning guide wireis advanced in the side-branch vessel, the catheter is again advancedand the stent is implanted in the main vessel in a manner similar tothat described for other embodiments. The catheter of FIGS. 20A-20C isdesigned to allow deployment of a stent very near but not “snowplowing”a bifurcation or side branch and is configured for treating bifurcationsas depicted in FIGS. 23A-25B. A commonly encountered situation in whichcatheter 70 would be used is an LAD that has disease right at andproximal to the diagonal take-off. After a careful look at multipleviews, the physician should be convinced that the diagonal is spared,but the lesion is very close and or immediately adjacent to the diagonaltake-off, as shown in FIG. 20D. It is very difficult to position astandard stent in the LAD and be certain that the lesion is fullycovered and the diagonal is not snowplowed or jailed. The catheter 70,having one wire in the LAD (main vessel) and the other in the diagonal(side-branch vessel), would allow precise definition of the bifurcationand avoid these problems. Square stent 78A, which has both endstransverse to the stent axis, could be deployed just proximal to thecarina, in which case the stent distal end may need to be flared a bit,or more likely, relaxed back to where the positioning guide wire 77 isresting against the proximal aspect of the ostium, visually defining theostium in relationship to the stent and allowing precise deployment.

Several alternative embodiments of main-vessel catheter 70 shown in FIG.20A, are depicted in FIGS. 20E, 21 and 22. The catheter device shown inFIG. 20E is similar to that shown in FIG. 20A, with the exception thatramp 57 is employed just distal of the distal end of the guide wirelumen 74 so that as guide wire 77 exits the lumen, it will moveoutwardly along ramp 57 so that it more easily advances into theside-branch vessel. Likewise, as shown in FIGS. 21 and 22, which aresimilar to the catheter described and depicted in FIGS. 20B and 20C, itis intended that guide wire 77 move outwardly so that it can more easilybe advanced into the side-branch vessel. In that regard, the distal endof guide wire lumen 74 is biased outwardly as shown in FIG. 22, so thatas the guide wire 77 is pulled back from lumen 75, the distal end ofguide wire lumen 74 will spring outwardly thereby assisting guide wire77 in moving radially outwardly to be positioned in the side-branchvessel.

In order to implant a square main-vessel stent 78A in a main vessel,where the disease is at or just proximal to the side-branch vessel,catheter 70 as depicted in FIGS. 21 and 22 is well suited. For example,catheter 70 is advanced over wire 77 until the catheter is positionedjust proximal of the side-branch vessel. Guide wire 73, which up to thispoint has been contained within catheter 70, is advanced into the mainvessel so that it is distal of the side-branch vessel. Guide wire 77 isthen withdrawn proximally so that its distal end 77A is withdrawn fromlumen 75, whereupon wire 77 and the distal end of guide wire lumen 74spring outwardly thereby assisting the positioning of guide wire 77 intothe side-branch vessel. The wire is then advanced into the side-branchvessel and catheter 77 is advanced so that wire 77 rests on the proximalostium of the side-branch vessel, wherein square stent 78A can then beexpanded to cover the diseased portion, but not span or cover (jail) theopening to the side-branch vessel.

If the diseased portion of a main vessel is directly adjacent theopening to the side-branch vessel, as depicted in FIG. 20F then thecatheter system as depicted in FIG. 20A can be incorporated only itwould implant distal angled stent 78B. As shown in FIG. 20F, stent 78Bhas an angle at its distal end which coincides with the opening to theside-branch vessel so that the diseased portion of the main vessel iscovered by the distal end of the stent, with the angle of the stentangled proximally so that the side-branch vessel is not covered orjailed. Various alternatives of square stent 78A and distal angled stent78B are used for treating various conditions as depicted in FIGS. 23Athrough 26B.

In another alternative embodiment as depicted in FIGS. 27-33, a dualballoon Y-shaped catheter assembly is provided to stent a bifurcation.In this embodiment, a Y-shaped stent is implanted to cover thebifurcation. Catheter 90 includes first and second expandable members91,92 that are configured to reside side by side (Y-shaped) for lowprofile delivery and to spring apart for implanting the stents. Lockingring 93 may be used to assist in holding the expandable members togetheruntil just prior to use, at which time it is removed. A guide wire lumen95 extends at least through a portion of the catheter and slidablyreceives guide wire 96. Guide wire lumen 98 extends at least through aportion of the catheter and slidably receives guide wire 99. Guide wirelumen 98 includes distal section 98A and 98B. A Y-shaped stent 100 ismounted on the first and second expandable members 91, 92.

In one method of stenting the bifurcated vessels, as shown in FIGS. 29to 33, guide wire 99, previously positioned distal to the bifurcation inone limb (perhaps the most vulnerable to problems for wire recrossing),is back loaded into lumens 98A and 98B and catheter 90 is advanced overwire 99 so that the catheter is advanced distally beyond thebifurcation. Guide wire 96 which has been contained in lumen 95 to thispoint, is carried in lumen 95 as the catheter is advanced along guidewire 99. Wire 99 is then withdrawn until its distal end pulls out of thedistal section 98A. As guide wire 99 is pulled back (proximally), thefirst and second expandable members 91,92, which are normally biasedapart, are released and now spring apart. The wire whose lumen is mostdistant (lateral) to the bifurcation (in this case wire 96) is thenadvanced into the distal vessel and the other wire (in this case 99)withdrawn as seen in FIG. 29B. The catheter is then withdrawn proximallyso that the expandable members 91,92 are now proximal to the bifurcationas depicted in FIG. 29C and the other guide wire (in this case wire 99)advanced into the other limb of the bifurcation as shown in FIG. 30.Catheter 90 is then advanced distally over both guide wires 96 and 99,as shown in FIG. 31, until stent 100 is positioned in the bifurcation ofthe intersection of the vessels 105,106. Due to the appropriate wireselection, rotation of no more than 90° will be required. Stent 100 isimplanted by inflating expandable members 91,92 in a known manner. Theexpandable members are then deflated, and the catheter is withdrawn fromthe patient. The novel arrangement of guide wires 96 and 99 and theirrespective lumens permit single unit transport of a Y stent to thedistal target site without wire wrapping problems and it allows forminimal requirements of rotation of the device (less than 90°) foroptimal deployment (allowing minimal twist deformity). The guide wiresmay be left in place for further intervention such as finishing thestents with simultaneous high pressure balloon inflation.

Referring to FIGS. 37-41, in yet another alternative embodiment, thedual balloon Y-shaped catheter assembly may include a restraining membersuch as mandril 120. The mandril is positioned within lumens 98A and98B. It is also contemplated that an assembly can be used having twoseparate balloons that inflate simultaneously. The mandril should bestiff enough to secure expandable members 91,92 to each other. Themandril may extend distally of expandable member 92 and have anatraumatic distal tip. Alternatively, it is contemplated that lumen 98Acan be sealed at its distal end. If desired, locking ring 93 can be usedto assist in holding the expandable members together until just prior touse, at which time it is removed.

In use, guide wire 96, previously positioned distal to the bifurcationin one limb, is back loaded into lumen 95 and catheter 90 is advancedover wire 96 so that the catheter is advanced to a location proximatethe bifurcation. The mandril 120 is carried in lumens 98A and 98B as thecatheter is advanced along guide wire 96. When the catheter reaches thebifurcation, the mandril 120 can be withdrawn until its distal end pullsout of distal section 98A. As the mandril is retracted (proximally),expandable members 91,92, which are normally biased apart, are releasedand spring apart, as illustrated in FIG. 39. The mandril 120 may now beremoved from the patient and guide wire 122 inserted into lumen 98B. Theguide wire 122 may then be advanced into the other limb of thebifurcation as shown in FIG. 40. Alternatively, the mandril may be aguide wire or guide wire-like element, and may itself be advanced intothe limb, thus eliminating the need for guide wire 122.

Catheter 90 is then advanced distally over guide wire 96 and guide wire122 (or mandril 120), until stent 100 is properly positioned in thebifurcation. Stent 100 is implanted by inflating expandable members91,92 in a known manner. The expandable members are then deflated, andthe catheter is withdrawn from the patient.

In an alternative embodiment of the invention, a pair of stents havingvarying stent cell density are implanted in a bifurcated vessel, asdepicted in FIGS. 34-36C.

As shown in FIG. 34, apertured stent 115 is provided in which aperture116 is positioned on its outer surface. Stent 115 includes heavy stentcell density 117 and light stent cell density 118 along its outersurface. As can be seen in FIG. 35, two stents 115 have been combined sothat the light density of one overlaps the light density of the othercausing the combined stents to create relatively uniform heavy celldensity and thus providing relatively uniform heavy cell density overthe entire bifurcated vessel wall.

As shown in FIGS. 36A to 36C, two stents 115 are implanted to stent thebifurcation. For sake of clarity, as shown in FIG. 36A, apertured stent115 shown implanted in the main vessel such that aperture 116 spans andprovides an opening to the side-branch vessel while heavy stent celldensity 117 provides full coverage of the distal main vessel by stent115. As depicted in FIG. 36B, apertured stent 115 is partially implantedin the side-branch vessel and partially implanted in the main vessel, inthis case with aperture 116 facing the continuing lumen of the mainvessel. More specifically, heavy stent cell density portion 117 isimplanted in the side-branch vessel, while light stent cell density 118is implanted in the main vessel, with aperture 116 providing an openingfor blood flow through the main vessel. It is intended that stent 115 beimplanted first as seen in FIG. 36A and that a second stent 115subsequently be implanted as shown in 36B or, by physician preference,this sequence may be reversed. Thus, in FIG. 36C, both stents 115 havebeen implanted, and both apertures 116 provide openings so that bloodflow is unimpaired through both main vessel and side-branch vessel andno stent struts are left unopposed. The light stent cell densityportions 118 of both 115 stents overlap proximal to the bifurcation,thereby insuring that there is full coverage of the bifurcated area byheavy stent cell density. Both stents 115 are implanted with thecatheter delivery system described herein which includes a positioningwire to accurately position and implant the stents in the bifurcatedvessels.

While the invention herein has been illustrated and described in termsof an apparatus and method for stenting bifurcated vessels, it will beapparent to those skilled in the art that the stents and deliverysystems herein can be used in the coronary arteries, veins and otherarteries throughout the patient's vascular system. Certain dimensionsand materials of manufacture have been described herein, and can bemodified without departing from the spirit and scope of the invention.

What is claimed is:
 1. A stent delivery assembly for implanting a stentin a bifurcated vessel having a side-branch vessel and a main vessel,comprising: a dual balloon Y-shaped catheter having a proximal end and adistal end, the catheter including a single catheter shaft joining apair of relatively short catheter shaft portions, a first expandablemember having a proximal end and a distal end and a second expandablemember having a proximal end and a distal end; a first lumen forreceiving a restraining member, the first lumen extending through atleast a portion of the catheter including the first expandable member; asecond lumen for receiving a guide wire, the second lumen extendingthrough at least a portion of the catheter including the secondexpandable member; and a restraining member positioned within the firstlumen; wherein the first expandable member and the second expandablemember are normally biased apart, but are restrained and held togetherby the restraining member to provide a low profile during delivery ofthe stent.
 2. The stent delivery assembly of claim 1, wherein therestraining member is a mandrel.
 3. The stent delivery assembly of claim1, wherein the restraining member is a guide wire.
 4. The stent deliveryassembly of claim 1, wherein a stent is removably mounted on the firstand second expandable members.
 5. The stent delivery assembly of claim1, further including a removable locking ring for assisting in holdingthe distal ends of the first expandable member and the second expandablemember together prior to implantation of the stent.
 6. The stentdelivery assembly of claim 1, wherein the first lumen includes a distalsection, a portion of which extends through at least a portion of thesecond expandable member.
 7. The stent delivery assembly of claim 6,wherein the restraining member extends through the first lumen found onthe first expandable member and a portion of the lumen on the secondexpandable member to hold the first and second expandable memberstogether until the assembly is to be deployed.